Using a chemical vapor-deposition technique, a research team from Pennsylvania State University in University Park and the Center for Applied Energy Research in Lexington, Ky., has fabricated ruthenium-doped multiwall carbon nanotubes that photoluminesce at 515 nm.The researchers predict that the method, reported in the Dec. 10 issue of Applied Physics Letters, may be applied to other transition-metal and rare-earth elements to produce different frequencies of luminescence, potentially leading to display applications with pixel sizes down to 10 nm. The team is considering pursuing such applications commercially.